1. Field of the Invention
The invention relates generally to an air filter for an internal combustion engine. More specifically, the invention relates to an air cleaner having a primary inlet defining a primary passage and a secondary inlet defining a bypass passage that is opened when an airflow through the primary passage is lower than a critical level.
2. Related Technology
Air cleaners for internal combustion engines typically have an inlet positioned such that ambient air can flow unhindered into the air cleaner. Therefore, the air inlet is typically situated behind a radiator grill of the vehicle or in the vicinity of a fender. However, when the vehicle is operated in a heavy or blowing snowfall, snow can be aspirated into the air inlet and accumulate within the air filter housing. If a sufficient amount accumulates, the snow can obstruct the air filter inlet and may partially or completely obstruct air flow to the engine. Furthermore, when the vehicle experiences temperature changes, such as being moved in and out of a heated enclosure, the accumulated snow can melt and refreeze to form a layer of ice that interrupts the air supply to the engine.
In order to overcome the effects of an obstructed inlet, current air intake systems include a primary air inlet defining a primary opening into the air chamber and a secondary air inlet defining a second opening into the air chamber; the secondary inlet being positioned away from the front of the vehicle. However, during heavy snowfall, the secondary air inlet may become obstructed by swirling snow particles in a manner similar to that described above with respect to the primary inlet and snow from either inlet may obstruct the other.
One air intake system currently known in the art also includes a door positioned so as to substantially prevent air flow through the secondary inlet, except when desired to reduce noise, vibrations and harshness (NVH) and to improve engine efficiency. However, multiple, redundant air inlets may undesirably increase the air intake system NVH. Additionally, a secondary inlet door adds many different components, such as springs and multiple-component hinges, thus increasing part complexity.
Additionally, cool air is denser and thus provides more efficient engine operation than warm air. Therefore, it is desirable to draw cool, ambient air into the air intake system rather than air that has been heated by vehicle components.
In view of the above, it is desirous to provide an air intake system with a secondary inlet that does not become obstructed by snow entering through the primary inlet and that includes a simple mechanism for preventing airflow through the secondary inlet when not desired.